Adhesives comprising epoxy-acid crosslinked groups and methods

Abstract

Adhesives compositions and methods of preparing adhesive compositions are described. The methods generally comprise a) providing a syrup composition comprising i) a free-radically polymerizable solvent monomer; and ii) a solute (meth)acrylic copolymer; and b) radiation curing the syrup composition in the absence of an ionic photoacid generator. In one embodiment, the solute (meth)acrylic copolymer as provided or during curing comprises repeat units derived from at least one alkyl(meth)acrylate monomer, at least one ethylenically unsaturated monomer comprising an acid-functional group; and at least one (meth)acryloyl monomer comprising an epoxy-functional group; and the acid-functional groups crosslink with the epoxy-functional groups. In another embodiment, the solute (meth)acrylic copolymer comprising repeat units derived from at least one alkyl(meth)acrylate monomer and at least one ethylenically unsaturated monomer comprising an acid-functional group; and an epoxy resin, having on average greater than one polymerizable epoxy group per molecule, crosslinks the acid-functional groups.

What is claimed is: 
     
       1. A method of preparing an adhesive composition comprising:
 a) providing a syrup composition comprising
 i) a free-radically polymerizable solvent monomer; 
 ii) a solute (meth)acrylic copolymer comprising repeat units derived from
 at least one alkyl(meth)acrylate monomer, and 
 at least one ethylenically unsaturated monomer comprising an acid-functional group; 
 optionally at least one (meth)acryloyl monomer comprising an epoxy-functional group 
 
 iii) an epoxy resin having on average greater than one polymerizable epoxy group per molecule; and 
 
 b) radiation curing the syrup composition in the absence of an ionic photoacid generator and multifunctional(meth)acrylate monomer such that the epoxy resin crosslinks the acid-functional groups. 
 
     
     
       2. The method of  claim 1  wherein the syrup comprises 0.1 to 10 wt-% of ethylenically unsaturated monomer(s) comprising an acid-functional group. 
     
     
       3. The method of  claim 1  wherein the acid-functional group is a carboxylic acid group. 
     
     
       4. The method of  claim 1  wherein the ethylenically unsaturated monomer comprising an acid-functional group is acrylic acid or (meth)acrylic acid. 
     
     
       5. The method of  claim 1  wherein the (meth)acrylic copolymer comprises 0.1 to 5 wt-% of (meth)acryloyl monomer comprising an epoxy-functional group. 
     
     
       6. The method of  claim 1  wherein the (meth)acryloyl monomer comprising an epoxy-functional group is of the formula: 
       
         
           
           
               
               
           
         
         wherein: 
         R 7  is —H or C 1 -C 4  alkyl; 
         X 1  is —NR 9 — or —O—; and 
         R 8  is an epoxy-substituted (hetero)hydrocarbyl group. 
       
     
     
       7. The method of  claim 1  wherein the (meth)acryloyl monomer comprising an epoxy-functional group is of the formula: 
       
         
           
           
               
               
           
         
         wherein: 
         R 10  is a (hetero)hydrocarbyl group, preferably a hydrocarbyl group; 
         R 11  is —H or C 1 -C 4  alkyl; and 
         X 2  is —NR 12 — or —O—. 
       
     
     
       8. The method of  claim 1  wherein the syrup comprises at least 50 wt-% of (meth)acrylic acid ester monomers having a Tg less than 0° C. 
     
     
       9. The method of  claim 1  wherein the adhesive is a pressure sensitive adhesive. 
     
     
       10. The method of  claim 1  wherein the syrup comprises a photoinitiator. 
     
     
       11. The method of  claim 1  wherein the solute (meth)acrylic copolymer is prepared by copolymerizing the alkyl (meth)acrylate monomer, the ethylenically unsaturated monomer comprising an acid-functional group; and the monomer comprising an epoxy-functional group. 
     
     
       12. The method of  claim 1  wherein the solute (meth)acrylic copolymer is prepared by copolymerizing the alkyl (meth)acrylate monomer and the ethylenically unsaturated monomer comprising an acid-functional group; and the monomer comprising an epoxy-functional group is added prior to radiation curing. 
     
     
       13. The method of  claim 1  wherein the solute (meth)acrylic copolymer is prepared by copolymerizing the alkyl (meth)acrylate monomer and the monomer comprising an epoxy-functional group; and the ethylenically unsaturated monomer comprising an acid-functional group is added prior to radiation curing. 
     
     
       14. The method of  claim 1  wherein the radiation curing comprises exposing the syrup to ultraviolet radiation. 
     
     
       15. The method of  claim 1  wherein the syrup is applied to a substrate prior to radiation curing. 
     
     
       16. The method of  claim 1  wherein the adhesive composition comprises 0.5 to 3 wt-% of epoxy resin. 
     
     
       17. The method of  claim 1  wherein the acid-functional group of the solute (meth)acrylic copolymer directly ring opens the epoxy group forming a crosslink.